The present invention relates to a splined connection and particularly to elements which orient the shaft and hub connected and also seal that connection.
Splined connections are used in various applications in connection with torque transmission. Splined connections are particularly advantageous in cases where axial mobility between components is required. A splined connection usually comprises a shaft-shaped element provided with longitudinal protruding ridges and intermediate grooves, and a hub-shaped element provided with correspondingly shaped ridges and intermediate grooves and intended to be fitted in engagement with the ridges and grooves of the shaft so that a connection region causing the shaft and hub to rotate together is formed between them.
An example of such an application is in connection with transmission of torque from an engine to a power takeoff of a vehicle. In such cases the power takeoff may be connected to the engine's flywheel via the hub of the splined connection. The power takeoff is thus driven directly by the engine independently of the clutch. The splined connection is then situated inside a housing which encloses the clutch. The shaft will be hollow so that it can extend externally about the vehicle's input shaft to the gearbox. To enable the gearbox to be fitted, the splined connection region between hub and shaft needs to exhibit a certain amount of clearance.
A problem with such clearance between the hub and the shaft is that lubricant supplied to the connection region is readily ejected during operation. The space in the clutch housing also makes oil lubrication of the connection region impossible and grease lubrication can only be supplied sparingly, to avoid risk of grease reaching clutch plates situated in the vicinity of the splined connection. The space in the clutch housing contains a great deal of dust and particles. There is risk of such particles entering the connection region. The risk of particles accumulating in the connection region increases with the magnitude of the clearance. Finally, said clearance between hub and shaft allows obliqueness and radial displacement of the shaft relative to the hub. It is usual for such obliqueness and radial displacement to occur particularly at low load of the power takeoff. Obliqueness and radial displacement result in relative movement between hub and shaft in the connection region, causing wear of the surfaces in the splined connection region.
U.S. Pat. No. 4,126,018 refers to a spindle device intended to connect two rotating shafts. The spindle device comprises a spindle connected to two separate hubs in different splined connection regions. Each of the two hubs comprises a sealing device situated at an end portion of the region of connection of the respective hub to the spindle. However, the sealing devices do not seem to extend all the way down into the grooves between the ridges of the spindle. They therefore do not come into contact with the bottom surfaces of the grooves. This means that there is no absolute seal between spindle and hub in the splined connection regions. Each of the hubs is thus supported at only an end portion of a sealing device. A sealing device applied in this way does not provide stable support to prevent possible obliqueness of the hubs relative to the spindle.
U.S. Pat. No. 4,475,737 refers to a splined connection in a driveline. The splined connection comprises an annular seal arranged between a hub and a shaft at a relatively large distance from a connection region between the hub and the shaft. A sealing plug is arranged on the opposite side of the connection region. The plug is fastened so that it covers an end aperture in the hub. The shaft does not extend right up to the plug, which means that the plug provides no support surface for the shaft. There is thus risk of the shaft being at an angle to the hub during operation, particularly if the clearance between hub and shaft is large.